Device and method for preparing an electrochemical sensor

ABSTRACT

The invention relates to a device ( 1 ) for preparing an electrochemical sensor ( 2 ) enabling the sensor head ( 2   a ) thereof to be provided with an electrolyte ( 3 ) and a membrane ( 4 ). The inventive device comprises retaining means ( 6 ) for the sensor in addition to means for depositing the electrolyte ( 7 ) and means for depositing the membrane ( 8 ).

The invention relates to an apparatus for the preparation of anelectrochemical sensor in accordance with the preamble of claim 1. Theinvention further relates to a method for the preparation of anelectrochemical sensor in accordance with the preamble of claim 19.

Electrochemical sensors are known, the measuring principle of which isbased on ion diffusion. This ion diffusion takes place, using a suitableelectrolyte, usually via a semi-permeable membrane, for example a glassfor H⁺ and Teflon for CO₂. Such electrochemical sensors enable primarilythe H⁺-concentration to be measured and indirectly, via the measurementof the H⁺-concentration, also the concentration of, for example, CO₂ orO₂ to be determined. The measurement of the H⁺-concentration takes placewith a pH electrode, also termed a glass electrode.

A modification of the pH electrode is the pO₂ electrode, also termed aClark electrode, which serves for the measurement of the O₂concentration.

A further modification of the pH electrode is the pCO₂ electrode alsotermed a Severinghaus electrode which permits the measurement of the CO₂concentration. In the Severinghaus electrode the CO₂ diffuses through amembrane (Teflon) into an electrolyte with an NaHCO₃ solution with:CO₂+H₂O<−>H₂CO₃<−>H⁺+HCO₃ applying. The H⁺-concentration is measuredwith the pH electrode and the CO₂ value derived therefrom.

Such electrochemical sensors are used amongst other things for themeasurement of blood gas values such as the CO₂ concentration or the O₂concentration in the blood. The electrochemical sensor is applied to aposition of the human body with a good circulation of blood in order tomeasure the transcutaneous carbon dioxide partial pressure (tCpCO₂) orthe transcutaneous oxygen partial pressure (tcpO₂). Extensiveinformation concerning these generally known measurement methods are forexample to be found in the following review article “NoninvasiveAssessment of Blood Gases, State of the Art” by J. S. Clark et al., Am.Rev. Resp. Dis., Vol. 145, 1992, pp 220-232.

It is also known to provide the electrochemical sensor with additionalsensors, for example with LEDs and photoelectric sensors in order tosimultaneously carry out a pulsoximetric measurement. A combinationsensor of this kind for the combined measurement of the oxygensaturation of the haemoglobin in arterial blood and also of the arterialcarbon dioxide partial pressure is known from the document EP 0 267 978A1. This combination sensor includes as an electrochemical sensor, aSeveringhaus electrode for the measurement of the transcutaneous CO₂partial pressure and also an arrangement for the measurement of theoxygen saturation (SpO₂) by means of pulsoximetry.

A disadvantage of electrochemical sensors is the fact that theirpreparation and maintenance is very demanding and requires trainedspecialist personal. For the Severinghaus electrode the semi-permeablemembrane and the electrolyte which is located between the membrane andthe sensor head must, for example, be regularly exchanged in order toensure a problem-free operation. This servicing work is very demandingbecause the measurement accuracy is dependent on the thickness ofelectrolyte layer and also on the precise arrangement of the membrane.The reproducability of the measurement accuracy is of centralimportance, because vital parameters, such as the CO₂ content in bloodare measured with the electrochemical sensor. A faulty measurement ofthis parameter could prove lethal for a patient. The electrochemicalsensor is, moreover, frequently used in a hectic environment, such as inan intensive care station in the hospital. The electrochemical sensor ishowever also increasingly frequently used in the home area (home care)in order to monitor patients at home.

It is thus the object of the present invention to design the preparationof the electrochemical sensor reliably and simply.

This object is satisfied with an apparatus for the preparation of anelectrochemical sensor having the features of claim 1. The subordinateclaims 2 to 14 relate to further advantageously designed apparatuses.The object is further satisfied with a common carrier for the apparatushaving the features of the claims 15 to 18. The object is further solvedwith a method for the preparation of electrochemical sensor having thefeatures of claim 19. The subordinate claims 20 to 22 relate to furtheradvantageous method steps.

The invention is in particular solved with an apparatus for thepreparation of an electrochemical sensor in order to provide its sensorhead with electrolyte and a membrane comprising a holding means for thesensor, a means for the dispensing of the electrolyte and also a meansfor the dispensing of the membrane.

The holding means, the means for the dispensing of the electrolyte andalso the means for the dispensing of the membrane are jointly arrangedin the same apparatus, which has the advantage that the sensor head canbe reproducibly and very precisely provided with the electrolyte andalso equipped with the membrane. The apparatus is preferably designedsuch that the sequence of preparation of this sensor is compulsorilyguided in that first the electrolyte is dispensed and thereafter thesensor head can be equipped with the membrane.

The holding means, the means for the dispensing of the electrolyte andalso the means for the dispensing of the membrane are advantageouslyarranged within a common housing, so that they are not accessible fromthe outside during the preparation of the sensor.

The means for the dispensing of the membrane and for the placement ofthe same of the sensor head preferably has a spring which is arrangedsuch that the membrane is dispensed with a reproducible pressing forceonto the sensor head and secured to it. Moreover, the means for thedispensing of the membrane advantageously has a pressing body with apressing surface which, during the dispensing of the membrane, arealycontacts the membrane in order to reproducibly displace the electrolytelocated between the membrane and the sensor head in such a way that thesensor connected to the membrane has a reproducible layer thickness ofelectrolyte, in particular a uniform layer thickness of electrolyte,between the sensor head and the membrane. This apparatus has thedecisive advantage that every sensor equipped with the membrane has anessentially identical layer thickness of electrolyte. This increases themeasurement reliability and reduces faulty measurements. The apparatusof the invention has the advantage that the preparation of theelectrochemical sensor is essentially determined by the characteristicsof the apparatus and no longer by the experience and ability of aspecialist. Thus, even in a stress situation, such as, for example,results at an intensive care station, a reliable preparation of theelectrochemical sensor is ensured. Moreover, it is also possible for aninexperienced person to reliably prepare the sensor, for example in thehome area.

The apparatus of the invention also has, in a preferred embodiment, ameans for cleaning the sensor head and also a means for the removal ofan old membrane. An already used sensor can thus be put into theapparatus of the invention, wherein, with compulsory guidance the oldmembrane is first removed from the sensor, thereafter the sensor head iscleaned, the sensor head is provided with electrolyte and finally thesensor is provided with a new membrane.

In an advantageous design all consumed parts which are required for thepreparation of the electrochemical sensor are arranged in a commoncarrier, with this carrier being designed as an exchangeable partpreferably as a disposable or throw-away part. In this connection, priorto each preparation of an electrochemical sensor a new common carrier isfirst to be laid into the apparatus of the invention.

It is however also possible to conceive the entire apparatus of theinvention as a disposable part or throw-away part so that no commoncarrier has to be exchanged. This apparatus contains all the meansrequired for the preparation of an electrochemical sensor and does nottherefore have to be opened. This apparatus is thus particularly simpleto operate.

The invention will be described with reference to embodiments. There areshown:

FIG. 1 a a longitudinal section through an electrochemical sensorwithout a membrane set in place;

FIG. 1 b a longitudinal section through an electrochemical sensor with amembrane set in place;

FIG. 2 a side view of a schematically represented apparatus for thepreparation of an electrochemical sensor;

FIG. 3 a longitudinal section through a sensor held in a holding means;

FIG. 4 a longitudinal section through a means for the dispensing of theelectrolyte;

FIG. 5 a longitudinal section through a means for the dispensing of themembrane;

FIG. 6 a longitudinal section through a means for the cleaning of thesensor head;

FIG. 7 a side view of the means for the cleaning of the sensor head;

FIG. 8 a longitudinal section through a means for the removal of themembrane;

FIG. 9 a view onto a common carrier;

FIG. 10 a cross-section through an apparatus for the preparation of anelectrochemical sensor;

FIG. 11 a side view of the housing of the apparatus for the preparationof the sensor;

FIG. 12 a view onto the housing of the apparatus for the preparation ofthe sensor;

FIG. 13 a perspective view of the common carrier;

FIG. 14 a further perspective view of the common carrier;

FIG. 15 a partial view of the section along the section line A-A of FIG.11.

In the following the same reference numerals will be used for the sameitems.

FIG. 1 a shows in a longitudinal section an electrochemical sensor 2with a sensor head 2 a, glass electrode 2 b, holding grooves 2 c, innerspace 2 d and cable 2 e. The components located in the interior of thesensor 2 are not shown. FIG. 1 b shows in a longitudinal section thesensor 2 illustrated in FIG. 1 a which is prepared for the measurementin that its sensor head 2 a is now covered with an electrolyte 3 and amembrane 4 with a holding ring 4 a is secured to its sensor head 2 a.The electrochemical sensor shown in FIG. 1 b could for example contain aClark electrode or a Severinghaus electrode.

FIG. 2 shows, in a side view, a schematically illustrated apparatus 1for the preparation of the electrochemical sensor 2. The apparatuscomprises a housing 5 consisting of a housing upper part 5 a and also ofa housing lower part 5 b, with the two housing parts 5 a, 5 b beingmutually displaceably mounted in the direction of the displacement t.The housing lower part 5 b has an opening 5 m behind which a holdingmeans 6 for the sensor 2 is arranged. In the housing upper part 5 athere is disposed a means 7 for the dispensing of the electrolyte andalso a means 8 for the dispensing of the membrane. These two means 7, 8are coupled to an actuating means 5 c in order to move the means 7, 8 inthe direction of displacement s and thereby to supply the electrolyte 3or the membrane 4 to the sensor 2 fixed in the holding means 6. Themeans 7, 8 are disposed in the interior of the housing 5.

FIG. 3 shows, in a longitudinal section, a sensor 2 which is held in theholding means 6 including an abutment part 6 a, a first holding part 6 band also a lug 6 c. The sensor 2 can be released from the holding means6 in that the lug 6 c is depressed and thereby the first holding part 6b released from the engagement in the sensor 2. It can proveadvantageous to close the opening 5 m shown in FIG. 2 with a secondholding part 6 d, with this holding part 6 d being so designed that itlies on the sensor 2 and additionally fixes it.

FIG. 4 shows a longitudinal section through a means 7 for the dispensingof the electrolyte 3. The means 6 comprises a container 7 d, filled withelectrolyte 7 e, which has a closure 7 f (for example with a ball). Thecontainer 7 d is mounted in an outlet and holding part 7 a. The outletand holding part 7 a can be connected via a web 7 c to a common carrier11. A pressure exerted downwardly onto the actuating means 5 c istransmitted via the cylinder-like projection 5 d onto the means 7 sothat this is first moved downwardly until the spacer 7 b contacts thesensor head 2 a. Thereafter the container 7 d is pressed into the outletand holding part 7 a, with the closure 7 f opening with acorrespondingly high internal pressure and the electrolyte 7 e flowingvia the passage of the outlet and holding part 7 a onto the surface ofthe sensor head 2 a. As soon as the pressure is taken from the actuatingmeans 5 c the means 7 moves upwardly again and the spacers 7 b no longerlie on the sensor head 2 a.

FIG. 5 shows a longitudinal section through a means 8 for the dispensingof the membrane 4. The means 8 comprises a holder 8 a with lugs 8 b forthe holding ring 4 a of the membrane 4. The means 8 further includes apiston 8 d which is displaceably mounted via the guide part 5 e andwhich is coupled via a spring 8 f to the movable housing upper part 5 cand which has at the bottom a pressing body 8 e with a contact pressuresurface 8 g which uniformly contacts the membrane 4. The means 8 can beconnected via the holding part 8 c to a common carrier 11. The pressureexerted downwardly onto the actuating means 5 c acts via the cylindricalprojections 5 d onto the spring 8 f so that the piston 8 d is moveddownwardly. During this movement the lugs 8 b enter into contact withthe sensor 2 and are thereby spread apart, so that the membrane 4 isreleased and thereafter secured to the sensor 2. During the mounting ofthe membrane 4 onto the sensor 2 a comparatively uniform areal forcelies over the whole membrane 4, brought about by the pressing body 8 e,so that the electrolyte 3 located between the sensor head 2 a and themembrane 4 is uniformly displaced outwardly before the membrane 4 isfixedly connected via the holding means 4 a to the sensor 2. The means 8has the advantage that the maximum pressing force of the pressing body 8e is essentially determined by the spring 8 f which has the consequencethat the membrane 4 is connected to the sensor 2 preferablyindependently or hardly dependently on the force acting on the movablehousing part 5 c. The force brought about by the spring 8 f isreproducible, which permits a uniform covering of the sensor 2 with themembrane 4. The sensor 2 has in particular a uniform reproducible layerthickness of electrolyte 3.

The apparatus shown in FIG. 2 could have the means 6, 7, 8 shown in theFIGS. 3, 4 and 5 in that the means 6 is arranged in the lower part 5 bof the housing and the means 7 and 8 are arranged in the upper part 5 aof the housing.

FIG. 6 shows a longitudinal section through a means 9 for the cleaningof the sensor head 2 a. The means 9 includes a holding part 9 a in whicha rotary piston 9 b with a cleaning cloth 9 d is displaceably mounted.The rotary piston 9 b is moreover coupled via a spring 9 c to theholding part 9 a. A pressure exerted downwardly onto the actuating means5 c is transmitted via the cylinder-like projection 5 d, which is guidedin the housing upper part 5 a, onto the means 9 so that the latter ismoved downwardly. During this movement the cleaning cloth 9 d contactsthe sensor head 2 a at some time so that the rotary piston 9 b is thrustinto the holding part 9 a as a result of the further movement. Therelative movement of the rotary piston 9 b with respect to the holdingpart 9 a causes, as can be seen in FIG. 7, a rotary movement of therotary piston 9 b. FIG. 7 shows in the side view the means 9 for thecleaning of the sensor head 2 a. The holding part 9 a has a slit 9 eextending obliquely in which a cam 9 f, which is fixedly connected tothe rotary piston 9 b, is displaceably mounted. If the cleaning cloth 9d now lies on the sensor head 2 a and the holding part 9 a is then movedfurther downwardly, then the rotary piston 9 b will be thrust into theholding part 9 a and the slit 9 e and the cam 9 f bring about a rotarymovement of the rotary piston 9 b and thus in particular of the cleaningcloth 9 d, so that the sensor head 2 a is particularly intensivelycleaned.

FIG. 8 shows a longitudinal section through a means 10 for the removalof the membrane 4 secured to a sensor 2. The means 10 includes a holdingmeans 10 a, a guide part 10 b and also a lateral holding means 10 c. Themeans 10 can be connected via a resilient connection means 11 a to acommon carrier 11. The sensor 2 with a membrane 4 is introduced into themeans 10 with the membrane 4 aligned upwardly so that the holding ring 4a of the membrane 4 is held in the lateral holding means 10 c.Thereafter, a force is exerted onto the membrane 4 via the actuatingmeans 5 c which is guided via the cylinder-like projection 5 d in thehousing upper part 5 a and also by the guide part 5 e. Through thisforce exerted by the projection 5 d the holding ring 4 a is separatedfrom the sensor 2. During this separation the holding means 6 shown inFIG. 3 is preferably arranged beneath the means 10 so that the sensor 2is held in the holding means 6 directly after the release of the holdingring 4 a.

The means 6, 7, 8, 9, 10 shown in the FIGS. 3 to 8 all serve for thepreparation of an electrochemical sensor 2. Preferably at least themeans 6, 7 and 8 are arranged in one apparatus 1 for the preparation ofthe electrochemical sensor 2 as shown in FIG. 2. it can also proveadvantageous to provide further means, such as the means 9 and 10. Allthese means 6, 7, 8, 9, 10 can be arranged in the most diverse manner inan apparatus 1 in order to enable a preparation of the sensor 2.

FIG. 9 shows a top view of a common carrier 11 on which the means 10 forthe removal of the membrane 4, the means 9 for the cleaning of thesensor head 2 a, the means 7 for the dispensing of the electrolyte 3 andalso the means 8 for the dispensing of the membrane 4 are arrangeddistributed in the peripheral direction. Of the means 8 only the holdingpart 8 c is shown.

FIG. 13 shows in a three-dimensional elevation a further embodiment of acommon carrier 11 with means 10, 9, 7 and 8 arranged distributed in theperipheral direction. The transparent membrane 4 with the holding ring 4a is mounted in the means 8 for the dispensing of the membrane. Thecarrier 11 showing in FIG. 13 includes all consumed parts which arerequired for the preparation of the electrochemical sensor 2. Thecarrier 11 is preferably designed as a disposable part, i.e. as athrow-away part. FIG. 14 shows the carrier 11 shown in FIG. 13 in a viewfrom below. The carrier 11 includes resilient connection means 11 a withwhich the means 8 and 10 are connected together and also a rigidconnection means 11 b with which the means 7 and 9 are connected. Thecarrier 11 further includes a first connection part 11 d, cams 11 c, asecond connection part 11 e and also a locking part 11 f.

FIG. 10 shows, in a cross-section, a particularly advantageouslydesigned apparatus 1 for the preparation of an electrochemical sensor 2.The same apparatus 1 is shown in FIG. 11 in a side view and in FIG. 12in the plan view. As is shown in FIG. 11 the housing 5 includes ahousing upper part 5 a and also a housing lower part 5 b which form twohalf shells within which the common carrier 11 and further componentsare arranged. The housing upper part 5 a has a plurality of holdingmeans 51 arranged distributed in the peripheral direction which engageinto the housing lower part 5 b in such a way that a bayonet connectionis formed thanks to which the two housing parts 5 a, 5 b can be mutuallyconnected and also released again. The bayonet connection is moreoverdesigned in such a way, and the holding means 51 are distributed in theperipheral direction in such a way, that the two housing parts 5 a, 5 bare mutually rotatably mounted. The housing 5 also includes a movablehousing upper part 5 c also termed actuating means which is displaceablymounted with respect to the housing upper part 5 a and also with respectto the housing lower part 5 b in the direction of movement s. A part ofthe sensor 2 projects into the opening 5 m and is located within theinterior of the housing 5. The plan view of FIG. 12 likewise shows ahousing 5 with the housing upper part 5 a and also with the actuatingmeans 5 c which is displaceably mounted relative to the latter. Thehousing upper part 5 a is moreover rotatably mounted, together with theactuating means 5 c in the direction of rotation D, with respect to thehousing lower part 5 b. The actuating means 5 c has markings A, B and Cat the surface. If the marking A is in the opening 5 m, then the sensor2 can, as shown, be introduced into the apparatus 1. Thereafter theactuating means 5 c is pressed downwardly in the direction of themovement s and thereafter relaxed upwardly again. Thereupon the housingupper part 5 a with the actuating means 5 c is turned in the directionof rotation D and the actuating means 5 c is pressed downwardly again inthe direction of movement s and relaxed upwardly again. This process isrepeated until the marking B is located at the opening 5 m. In thisposition of the actuating means 5 c the preparation of the sensor 2 iscompleted and it can be removed from the apparatus 1. Through a furtherrotation of the actuating means 5 c in the direction D the marking Creaches the opening 5 m. In this position the bayonet connection isunlatched and the housing 5 can be opened. Thereafter the common carriercan be removed from the housing 5 and replaced by a new common carrier11. The housing is put together again and the bayonet connection islatched so that the apparatus 1 is available for the preparation of afurther sensor 2.

FIG. 10 shows the actuating means 5 c which is displaceably mounted withrespect to the housing upper part 5 a in the direction of movement s,with a resetting spring 5 h being located at the center in order toalways bring the actuating means 5 c back into the illustrated basicposition again after a movement downwardly. The actuating means 5 cincludes a plurality of plungers 5 d which are formed as cylindricalprojections and which act on the means 7,8, 9 or 10. The holding means 6shown in FIG. 3, in which the sensor 2 can be firmly held, is arrangedin the housing lower part 5 b. The housing lower part 5 b also includesa pivot bearing 5 g in which a spigot 5 f of the housing upper part 5 ais rotatably mounted so that the housing upper part 5 a is rotatablymounted with respect to the housing lower part 5 b in the direction ofrotation D. The common carrier 11 is arranged in the internal space ofthe housing 5. The common carrier 11 is connected via a first connectingpart 11 d with the rotatable bearing 12. The rotatable bearing 12 ispressed upwardly by a spring 5 i. The carrier 11 is rotatably mountedwith respect to the housing lower part 5 b. The carrier 11 is moreoverconnected via a second eccentric connecting part 11 e to the housingupper part 5 a and coupled to the housing upper part 5 a with respect toa rotation in the direction D. The pivot bearing 5 g has at the outerside grooves 5 k extending in the direction s into which the cams 11 cengage during the movement in the direction s, so that the commoncarrier 11 and also the housing upper part 5 a is blocked during thismovement with respect to rotation in the direction D.

All the components illustrated in the FIGS. 3 to 8 are arranged in theapparatus 1 of FIG. 10, with only the apparatus 7 and 9 being explicitlyshown for the sake of simplicity of the illustration in FIG. 10, whereasthe apparatuses 8 and 10 are not shown. The carrier 11 arranged in FIG.10 is however in principle identical to the carrier 11 shown in FIGS. 13and 14 and thus includes the apparatuses 7, 8, 9 and 10.

The preparation of a electrochemical sensor 2 with the apparatus 1partly shown in FIG. 10 includes the following steps:

-   -   The bayonet connection of the two housing halves 5 a, 5 b is        opened, the common carrier 11 is removed, a new common carrier        11, such as is shown in the FIGS. 13 and 14 is inserted, the        bayonet connection of the two housing halves 5 a, 5 b is closed        again and the marking A of the actuating means 5 c turned to the        opening 5 m.    -   The sensor 2 shown in FIG. 1 b comprising a membrane 4 is        introduced into the inlet opening 5 m of the housing 5, with the        means 10 shown in FIG. 8 for the removal of the membrane 4 being        located behind the inlet opening 5 m. As soon as the sensor 2 is        introduced into the means 10 the actuating means 5 c is pressed        downwardly so that the cylinder-like projection 5 d releases the        sensor 2 from the holding ring 4 a and the sensor 2 is supplied        to the holding means 6 as shown in FIG. 10. The holding ring 4 a        with the membrane 4 remains in the means 10. Thereupon the        pressure on the actuating means 5 c is reduced or the actuating        means 5 c is fully released so that the actuating means 5 c        moves upwardly again into the base position shown in FIG. 10.    -   Thereupon the housing cover 5 a is rotated in the direction D        until the means 9 for the cleaning of the sensor head 2 a is        located above the sensor 2. The actuating means 5 c is then        pressed downwardly and the sensor head 2 a is cleaned, as        already described with respect to FIGS. 6 and 7, so that any        electrolyte eventually present on the sensor head 2 a is        removed. The actuating means 5 c is thereupon released again so        that it moves upwardly.    -   Thereupon the housing cover 5 a is turned in the direction D        until the means 7 for the dispensing of the electrolyte is        located over the sensor 2. The actuating means 5 c is then        pressed downwardly and the sensor head 2 a is provided with        electrolyte 3 as already described with respect to FIG. 4.        Thereafter the actuating means 5 c is released again so that it        moves upwardly.    -   Thereupon the housing cover 5 a is turned in the direction D        until the means 8 for the dispensing of the membrane 4 is        located above the sensor 2. The actuating means 5 c is then        pressed downwardly and the membrane 4 is connected to the sensor        2 as already described with the FIG. 5. Thereafter the actuating        means 5 c is released again so that it moves upwardly.    -   Thereupon the housing cover 5 a is turned in the direction D        until the marking B is located in front of the opening 5 m so        that the now completely prepared sensor 2 can be removed from        the apparatus 1 by renewed pressing and releasing of the housing        cover 5 a.    -   The housing cover 5 a is then turned further, until the marking        C is located in front of the opening 5 m. The bayonet connection        of the two housing halves 5 a, 5 b is thus unlocked, the common        carrier 11 can be removed, a new common carrier 11, as is shown        in FIGS. 13 and 14 can be inserted and the bayonet connection of        the two housing halves 5 a, 5 b can be closed again.    -   The apparatus 1 is now ready to prepare a further        electrochemical sensor 2.

In order to position the respective means 7, 8, 9, 10 precisely withrespect to the sensor 2 held in the holding means 6 during rotation ofthe housing cover 5 a the housing lower part 5 b has, as illustrated inFIG. 15 in a section A-A along the FIG. 11, inwardly projecting cams 5 non which the locking part 11 f of the common carrier 11 respectivelyabuts with its tongue 11 g. The cams 5 n are arranged distributed in theperipheral direction so that, on abutment of the locking part 11 f, therespective means 7, 8, 9, 10 is arranged precisely with respect to thesensor 2 so that the function corresponding to means 7, 8, 9, 10 can beexecuted at the sensor 2 by a downward pressing the actuating means 5 c.The tongue 11 g of the locking part 11 f is designed in such a way thatit comes to lie directly after the cam 5 n while the common carrier 11,after completely moving downwardly, moves upwardly again and is thus nolonger in engagement with the cam 5 n. Thus the housing cover 5 a isagain freely rotatably in the direction of rotation D until the lockingpart 11 f engages into the next projecting cam 5 n. This design causesthe actuation of the apparatus 1 to be compulsorily guided in that theoperation which has to take place for each step is preset. The housingcover 5 a is rotated in the direction of rotation D up to an abutment.Thereafter a movement of the actuating means 5 c, and associated with ita movement of common carrier 11 must necessarily take place in thedirection s. After the housing 5 is again located in the basic positionshown in FIG. 10 the cover 5 a can again be turned in the direction ofrotation D up to the next following abutment This compulsory guidanceensures that during the preparation of the sensor 2 no operation isforgotten. The apparatus 1 is thus particularly suited for use in anenvironment with high stress, for example at an intensive care stationor for a patient at home who hardly has experience with the preparationof an electrochemical sensor 2.

The embodiments of apparatuses for preparing an electrochemical sensor 2shown in the Figures represent embodiments from a plurality of designpossibilities in order to satisfy the required function of thepreparation of the sensor 2.

The apparatus 1 shown in FIG. 10 is also suitable to cover a sensor 2with a membrane 4 for the first time. The sensor 2 without membrane 4and holding ring 4 a is introduced for this purpose in the housingposition shown in FIG. 12 into the inlet opening 5 m of the housing 5and, by pressing the actuating means 5 c downwardly secured in theholding means 6 with the aid of the means 10. Thereafter, the apparatusis actuated further, as described in FIG. 10, so that the sensor 2 isprovided with electrolyte and membrane. As soon as the housing upperpart 5 a and also the actuating means 5 c have been turned sufficientlyfar that the marking B is located at the inlet opening 5 m the sensor 2is fully prepared.

The means 7, 8, 9, 10 may not all be arranged at the common carrier 11but can rather also be connected individually or in groups directly tothe housing 5.

In the above it has been described several times that the actuatingmeans 5 c is pressed in the direction downwardly with respect to theillustrated arrangement of the apparatus 1. The apparatus 1 can also befully held in the hand so that the actuating means 5 c is presseddownwardly with respect to the housing lower part 5 b. The termdownwardly not only means a vertical direction with respect to thesurface of the earth, but also a movement towards the housing lower part5 b.

1. Apparatus for the preparation of an electrochemical sensor in orderto provide a sensor head with an electrolyte and a membrane, theapparatus comprising a holding means for the sensor, a means fordispensing the electrolyte and a means for dispensing the membrane. 2.Apparatus in accordance with claim 1, wherein the holding means, themeans for dispensing the electrolyte and the means for dispensing themembrane are arranged within a common housing and wherein the means fordispensing the electrolyte and the means for dispensing the membrane aredisplaceably mounted with respect to the holding means.
 3. Apparatus inaccordance with claim 1, wherein the means for dispensing theelectrolyte and the means for dispensing the membrane are displaceablymounted with respect to the holding means and the means for dispensingthe electrolyte is positionable with respect to the holding means suchthat the electrolyte is able to be supplied to the sensor held in theholding means and the means for dispensing the membrane is able to bepositioned with respect to the holding means so that the membrane isable to be connected to the sensor held in the holding means. 4.Apparatus in accordance with claim 1, wherein the means for dispensingthe membrane is to dispense the membrane such that the membrane is ableto be secured to the sensor head with a reproducible pressing force. 5.Apparatus in accordance with claim 1, wherein the means for dispensingthe membrane includes at least a pressing body including at least apressing surface, wherein the pressing body is arranged such that thepressing surface contacts the membrane in a real manner during thedispensing of the membrane in order to displace electrolyte locatedbetween the membrane and the sensor head in such a way that the sensorconnected to the membrane has a reproducible layer thickness of theelectrolyte, between the sensor head and the membrane.
 6. Apparatus inaccordance with claim 1 comprising a means for the cleaning of thesensor head wherein the means for the cleaning of the sensor head isdisplaceably mounted with respect to the holding means, wherein themeans for cleaning is able to be so positioned with respect to theholding means so that the means for cleaning mechanically cleans thesensor head of the sensor held in the holding means.
 7. Apparatus inaccordance with claim 1, comprising a means for the removal of amembrane the means for the removal of a membrane being displaceablymounted with respect to the holding means, wherein the means for theremoval of the membrane is able to be positioned with respect to theholding means such that after the removal of a used membrane the sensoris able to be supplied to the holding means.
 8. Apparatus in accordancewith claim 1, wherein at least the means for the dispensing of theelectrolyte and the means for the dispensing of the membrane are securedto a common carrier, wherein the means for the cleaning and the meansfor the removal of the membrane are secured to the common carrier. 9.Apparatus in accordance with claim 1 comprising a housing with a housingbase and a housing cover wherein the holding means for the sensor isarranged in the housing base.
 10. Apparatus in accordance with claim 9,characterized in that the housing base and the housing cover are eachdesigned as a half shell which form a common inner space for thereception of at least the means for the dispensing of the electrolyteand of the means for the dispens-ing of the membrane and form a commoninner space for the reception of the holding means for the sensor, themeans for dispensing the electrolyte, the means for dispensing themembrane, a means for the cleaning of the sensor head and a means forthe removal of a membrane.
 11. Apparatus in accordance with claim 10wherein the housing base and the housing cover are releasablyconnectable to one another.
 12. Apparatus in accordance claim 10characterized in that the housing includes at least an actuating meansmovably disposed with respect to the housing cover which has anoperative connection to at least one of the means for dispensing theelectrolyte, the means for dispensing the membrane, the means for thecleaning of the sensor head and the means for the removal of a membranein order to bring about a force and/or a movement on at least one of themeans for dispensing the electrolyte, the means for dispensing themembrane, the means for the cleaning of the sensor head and the meansfor the removal of a membrane via the actuating means.
 13. Apparatus inaccordance with claim 12, wherein the actuating means is displaceablymounted essentially in the vertical direction with respect to thehousing cover.
 14. Apparatus in accordance with claim 8, wherein thecommon carrier is formed as an exchangeable part.
 15. A common carrierfor an apparatus in accordance with claim 1, comprising at least onecontainer filled with electrolyte and a membrane.
 16. A common carrierin accordance with claim 15, comprising a means for cleaning and a meansfor the removal of the membrane.
 17. A common carrier in accordance withclaim 15 comprising a first connection part which defines an axis ofrotation and and wherein the container and the membrane are arrangedspaced apart in a peripheral direction with respect to the axis ofrotation.
 18. A common carrier in accordance with claim 17, wherein themeans for the removal of the membrane, the means for cleaning, the meansfor the dispensing of the electrolyte and the means for the dispensingof the membrane are ar-ranged following one another in the peripheraldirection.
 19. A method for the preparation of an electrochemical sensorin order to provide a sensor head with an electrolyte and a membranecomprising securing a sensor in a holding means and in compulsory guidedmanner, applying at least the electrolyte onto the sensor head andproviding the sensor head with a membrane which covers the electrolyte.20. A method in accordance with claim 19, wherein the membrane issupplied to the sensor head with a reproducible pressing force definedby a spring in order to reproducibly displace electrolyte presentbetween the membrane and the sensor head in such a way that in each casea reproducible layer thickness of electrolyte arises between themembrane and the sensor head.
 21. A method in accordance with claim 19comprising removing the original membrane from the sensor head in acompulsory guided manner, cleaning the sensor head depositing theelectro-lyte on the sensor head and connecting a mem-brane to thesensor.
 22. A method in accordance with claim 21, wherein the compulsoryguidance takes place in such a way that the sensor is secured within ahousing and in that individual steps at the sensor are compulsorilyguided by rotation of a part of the housing.
 23. Apparatus in accordancewith claim 1, wherein the means for dispensing the membrane includes atleast a pressing body including at least a pressing surface, wherein thepressing body is arranged such that the pressing surface contacts themembrane in a real manner during the dispensing of the membrane in orderto displace electrolyte located between the membrane and the sensor headin such a way that the sensor connected to the membrane has areproducible layer thickness of the electrolyte and has a uniform alayer thickness of the electrolyte, between the sensor head and themembrane.
 24. Apparatus in accordance with claim 10 wherein the housingbase and the housing cover are releasably connectable to one another bya mutual rotary movement.
 25. Apparatus in accordance with claim 8,wherein the common carrier is formed as a disposable part.
 26. A commoncarrier in accordance with claim 15 comprising a first connection partwhich defines an axis of rotation wherein the container, the membrane, ameans for cleaning and a means for the removal of the membrane arearranged spaced apart in a peripheral direction with respect to the axisof rotation.